In the past, there has been used an optical coherent tomography diagnosis apparatus (OCT: Optical Coherent Tomography) for arteriosclerosis diagnosis, for diagnosis before the surgery under an endovascular treatment by a high performance catheter such as a balloon catheter, a stent and the like, or for confirming the result thereof.
An optical coherent tomography diagnosis apparatus is an apparatus in which, in a state in which a catheter with a built-in optical lens and an optical fiber mounted with an optical mirror at the distal tip thereof is positioned in a blood vessel, measuring light is light-emitted in the blood vessel while rotating the optical mirror, radial scanning is carried out by receiving reflected light from biological tissue and a tomographic image of the blood vessel is created based on the coherent light by the interference between the reflection light obtained by the radial scanning and reference light split from the measuring light beforehand.
Further, there has been developed recently an optical coherent tomography diagnosis apparatus which utilizes wavelength-sweeping as an improved type of optical coherent tomography diagnosis apparatus.
The basic structure of the wavelength-sweeping optical coherent tomography diagnosis apparatus is similar to that of the optical coherent tomography diagnosis apparatus (OCT). The wavelength-sweeping optical coherent tomography diagnosis uses a light source having a longer wavelength than that of the optical coherent tomography diagnosis apparatus and also continuously light-emits lights having different wavelengths. Then, the mechanism for varying the light path length of the reference light is made unnecessary by obtaining reflection light intensity at each point in the depth direction of the biological tissue by using frequency analysis of the coherent light.
Here, with respect to any of the optical coherent tomography diagnostic apparatuses mentioned above, the amount of light of the measuring light (or the reflection light) or of the reference light and also the coherence performance thereof will largely affect the quality of the cross-section image visualized. Consequently, it is desirable for the light path to be such that the amount of measuring light (or reflection light) or reference light and also the coherence performance thereof will maintain a certain standard level.
On the other hand, depending on a use environment of the optical coherent tomography diagnostic apparatus or a transportation environment under the delivery thereof, it happens that the amplification performance and the coherence performance of the light source deteriorates as a result of the fact that a continuous vibration or the like is applied to the apparatus. Also, the amount of light of the measuring light (or the reflection light) or the reference light and also the coherence performance might be lowered as a result of the fact that affection is exerted on the state of the connection, the loss or the polarization of the optical fiber which forms the light path. In this case, the quality of the cross-sectional image visualized on the basis of the coherent light may be deteriorated.
Generally, there is a possibility that the quality deterioration of the cross-sectional image might lead to a fault diagnosis even if the deterioration is very little, so that in a case in which there exists deterioration, it becomes necessary for a user (doctor) to take treatments (various kinds of adjustments) for improving the amplification performance and the coherence performance of the light source and also for improving the state of the connection, the loss and the polarization of the optical fiber by calling a service person immediately (see Patent Document 1: Japanese PCT unexamined publication No. 2001-527659). If the deterioration of the cross-sectional image is relatively little, the user (doctor) may not realize such fact and so it can be assumed that the diagnosis will continue while the deteriorated cross-sectional image state is maintained.